SPP1 and breast cancer: Shi et al. reported that osteopontin-c, a splice variant of OPN, supported the anchorage independence of invasive breast cancer cells by utilizing glucose to generate energy (Le et al., 2003; Vergis et al., 2008; Raja et al., 2014; Ostheimer et al., 2017; Cao et al., 2019; Nishio et al., 2021).